Recent developments with photo-cathode-based accelerators and light sources such as free electron lasers and x-ray laser machines have demonstrated the usefulness and desirability of lasers with extremely short pulses. With the rapid progress in the performance of the existing machines and many proposed facilities, the technical requirements for conventional lasers such as drive lasers, X-ray seed lasers and diagnostic lasers have reached a new level. However, the pulsed laser systems currently used in the art typically fall into one of two groups either high energy and relatively low repetition rate or relatively low energy and high repetition rate. Ti:sapphire lasers are exemplary of the former having a femto-second pulse width, milli-joule energy output pulse energy and kilo-hertz (kHz) repetition rate. Typically conventional lasers having repetition rates of mega-hertz (MHz) to giga-Hertz (GHz) have pulse energies on the level of nano-joules (nJ). Major obstacles have been encountered in attempting to achieve mega-hertz repetition rates on milli-joule energy output lasers such as Ti:sapphire lasers or micro-joule to milli-joule pulse energy outputs on a mega-hertz repetition rate laser system.
Additionally, for single oscillator lasers known in the art changing repetition rate is very difficult at best. In the prior art, the traditional master-oscillator-power amplifier mode (MOPA) configuration is most typically used. In the MOPA mode, the repetition rate is set by the oscillator. In the traditional system the output pulse energy is limited with a CW amplifier as the maximum stored energy in the CW amplifier is limited for efficient extraction and the amplified energy in each pulse is dependent on the pulse repetition rate with higher repetition rates typically yielding lower pulse energies.
Accordingly, there is a need for a practical way to achieve high pulse energy and high repetition rate in a pulsed laser system simultaneously.